I chose Pharo for a project recently (http://github.com/studio/studio/). I am enjoying using it in production. The Glamorous Toolkit framework (Inspector and Spotter) is saving me a huge amount of work.

I see Pharo as two universes: the stable (now Pharo 6) and the development (now Pharo 7.) I work on the stable one and I don't concern myself at all with what is happening on the development one. The yearly release cycle of development-to-stable feels about right to me.

I have had to spend some time working out how to fit Pharo into my wider project build system, and how to store Smalltalk source code on Github as part of a larger repository such that you can handle merges etc. This made me curse a lot. It worked out fine in the end though.

I have been working on this for one year now and I haven't had problems with Pharo bugs or instability.